Laser Beam Welding 激光焊

Laser Beam Welding is a fusion welding process in which two metal pieces are joined together by the use of laser. The laser beams are focused to the cavity between the two metal pieces to be joined. The laser beams have enough energy and when it strikes the metal pieces produces heat that melts the material from the two metal pieces and fills the cavity. After cooling a strong weld is formed between the two pieces.
激光焊接是利用激光将两个金属件连接在一起的熔焊工艺。激光束被聚焦到要连接的两块金属之间的空腔上。激光束有足够的能量,当它击中金属碎片时,产生的热量会融化两块金属碎片中的材料并填满空腔。冷却后,在两个部件之间形成牢固的缝。

It is a very efficient welding process and can be automated with robotics machinery easily. This welding technique is mostly used in automotive industry.
这是一个非常有效的焊接工艺,可以很容易与自动化与机器人机械结合。这种焊接技术主要应用于汽车工业。

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1 Principle 原理

Laser beam welding is a technique in manufacturing whereby two or more pieces of material (usually metal) are joined by together through use of a laser beam. Laser stands for Light Amplification by Stimulated Emission of Radiation. It is a non-contact process that requires access to the weld zone from one side of the parts being welded.
激光束焊接是一种制造技术,利用激光束将两块或两块以上的材料(通常是金属)连接在一起。激光是通过受激发射光放大的辐射。这是一种非接触过程,需要从焊接部件的一侧进入焊接区。

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2 Types 类型

2.1 Gas lasers 气体激光

Gas Laser use a mixture of gases such as helium and nitrogen. There are also CO2 or carbon dioxide lasers. These lasers use a low-current, high-voltage power source to excite the gas mixture using a lasing medium. Operate in a pulsed or continuous mode.
气体激光使用氦气和氮气等气体混合物。还有二氧化碳或二氧化碳激光器。这些激光器使用低电流高压电源使用激光介质激发气体混合物。以脉冲或连续模式运行。

Carbon dioxide lasers use a mixture of high purity carbon dioxide with helium and nitrogen as the lasing medium. CO2 lasers are also used in dual beam laser welding where the beam is split into two equal power beams.
二氧化碳激光器使用高纯度二氧化碳与氦和氮的混合物作为激光介质。CO2激光器也用于双光束激光焊接,其中光束被分成两个相等的功率光束。

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2.2 Solid state lasers 固态激光

2.2.1 Nd:YAG lasers

Nd:YAG lasers can operate in both pulsed and continuous mode, but the other types are limited to pulsed mode. The original and still popular solid-state design is a single crystal shaped as a rod approximately 20 mm in diameter and 200 mm long, and the ends are ground flat. This rod is surrounded by a flash tube containing xenon or krypton. When flashed, a pulse of light lasting about two milliseconds is emitted by the laser.
Nd:YAG激光器可以在脉冲模式和连续模式下工作,但其他类型的激光器仅限于脉冲模式。先前与现在任然流行的固态设计是一个单晶形状的棒状,直径约20毫米,长200毫米,两端磨平。这根棒被一个含有氙或氪的闪光管所包围。当闪光时,激光会发出持续约两毫秒的脉冲光。

Nd:YAG laser outputs between 0.04–6,000 W. To deliver the laser beam to the weld area, fiber optics are usually employed.
Nd:YAG激光输出在0.04-6,000W之间。为了将激光束传送到焊接区域,通常使用光纤。

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2.2.2 ruby lasers 红宝石激光

Ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. Ruby lasers produce pulses of coherent visible light at a wavelength of 694.3 nm, which is a deep red color. Typical ruby laser pulse lengths are on the order of a millisecond.
红宝石激光器是一种固态激光器,使用合成红宝石晶体作为增益介质。红宝石激光产生一种深红色波长为694.3nm的相干可见光脉冲。典型的红宝石激光脉冲长度约为毫秒。

A ruby laser most often consists of a ruby rod that must be pumped with very high energy, usually from a flashtube, to achieve a population inversion. The rod is often placed between two mirrors, forming an optical cavity, which oscillate the light produced by the ruby's fluorescence, causing stimulated emission.
红宝石激光器通常由红宝石杆组成,必须用非常高的能量泵送,通常来自闪光管,以实现粒子数反转。杆通常放置在两个镜子之间,形成光学腔,其振荡由红宝石的荧光产生的光,引起受激发射。

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2.3 Fiber laser 光纤激光

Fiber laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements. Fiber laser can be developed on the basis of fiber amplifier: under the action of pump light, the fiber is easy to form a high power density, causing the laser level of the laser working material "particle number inversion", when the appropriate addition of positive feedback loop (to form a resonator) can form laser oscillation output.
光纤激光器是以掺杂稀土元素的光纤为有源增益介质的激光器。光纤激光器可在光纤放大器的基础上开发:在泵浦光的作用下,纤维很容易形成高功率密度,造成激光工作物质的激光能级“粒子数反转”,当适当加入正反馈回路(构成谐振器)可以形成激光振荡输出。

In fiber lasers, the main medium is the optical fiber itself. They are capable of power up to 50 kW and are increasingly being used for robotic industrial welding.
在光纤激光器中,主要介质是光纤本身。它们的功率高达50 kW,并且越来越多地用于机器人工业焊接。

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3 Working 工作

  • First the setup of welding machine at the desired location (in between the two metal pieces to be joined) is done.
    首先,在所需位置(在待连接的两个金属件之间)完成焊接机的设置。

  • After setup, a high voltage power supply is applied on the laser machine. This starts the flash lamps of the machine and it emits light photons. The energy of the light photon is absorbed by the atoms of ruby crystal and electrons get excited to their higher energy level. When they return back to their ground state (lower Energy state) they emit a photon of light. This light photon again stimulates the excited electrons of the atom and produces two photons. This process keeps continue and we get a concentrated laser beam.
    安装完成后,在激光器上加高压电源。这启动了机器的闪光灯,并发出光子。光子的能量被红宝石晶体的原子吸收,电子被激发到更高的能级。当它们回到基态(低能态)时,就会发出光子。这个光光子再次刺激原子中被激发的电子并产生两个光子。这个过程继续下去,我们得到了一个集中的激光束。

  • This high concentrated laser beam is focused to the desired location for the welding of the multiple pieces together. Lens are used to focus the laser to the area where welding is needed. CAM is used to control the motion of the laser and workpiece table during the welding process.
    这种高度集中的激光束被聚焦到所需的位置,以便将多个部件焊接在一起。透镜用来把激光聚焦到需要焊接的地方。在焊接过程中,CAM用于控制激光和工件工作台的运动。

  • As the laser beam strikes the cavity between the two metal pieces to be joined, it melts the base metal from both the pieces and fuses them together. After solidification we get a strong weld.
    当激光束击中要连接的两块金属之间的空腔时,它会熔化两块金属的基本金属,并把它们熔合在一起。凝固后,我们得到一个牢固的焊缝。

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4 Applications 应用

  • Automotive manufacturing
    汽车制造
  • fiber laser welding in shipbuilding and marine engineering
    光纤激光焊在造船及海洋工程方面的应用
  • Aircraft manufacturing
    飞机制造
  • medicine
    医学

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5 Advantages and Disadvantages 有点和缺点

5.1 Advantages 优点

  • It produces high weld quality.
    焊接质量高
  • LBW can be easily automated with robotic machinery for large volume production.
    激光焊可通过机器人机械轻松实现自动化,实现大批量生产
  • No electrode is required.
    无需电极
  • No tool wears because it is a non-contact process.
    没有工具磨损,因为它是非接触工艺。
  • The time taken for welding thick section is reduced.
    减少焊接厚截面所需的时间
  • It is capable of welding in those areas which is not easily accessible.
    能够在不易接近的区域进行焊接。
  • It has the ability to weld metals with dissimilar physical properties.
    能够焊接具有不同物理特性的金属
  • It can be weld through air and no vacuum is required.
    能够在空气中焊接,不需要真空。
  • X – Ray shielding is not required as it does not produce any X-Rays.
    不需要X射线屏蔽,因为它不会产生任何X射线
  • It can be focused on small areas for welding. This is because of its narrower beam of high energy.
    能够专注于焊接的小区域,这是因为它的能量较窄。
  • Wide variety of materials can be welded by using laser beam welding.
    各种材料都可以通过使用激光焊接。
  • It produces weld of aspect ratio (i.e. depth to width ratio) of 10:1.
    能产生纵横比(即深宽比)为10:1的焊缝。

5.2 Disadvantages 缺点

  • Initial cost is high. The equipment used in LBW has high cost.
    初始成本很高,激光焊使用的设备成本高
  • High maintenance cost.
    维护成本高
  • Due to rapid rate of cooling, cracks may be produced in some metals.
    由于冷却速度快,某些金属可能会产生裂缝
  • High skilled labour is required to operate LBW.
    操作激光焊需要高技能工人
  • The welding thickness is limited to 19 mm.
    焊接厚度限制在19毫米
  • The energy conversion efficiency in LBW is very low. It is usually below 10 %.
    激光焊的能量转换效率非常低,通常低于10%